Heat has been and remains the most common method for bacterial destruction in many domains in general and particularly in food. The content of this book specially deals with thermoresistance of some Bacillus spores as related to sublethal heat treatment and, the subsequent relatively recent phenomenon named HIR (Heat-Induced Resistance). Due to the emerging applications of bacterial spores in various fields, the observations and analysis hereby contribute in the understanding of an aspect of nature and mechanisms of bacterial spores heat resistance. They should be of great interest for researchers and professionals in health and nutrition sectors, agro-based industries, and even those involved into biological warfare technologies. Finally, all scientists and professionals will find useful information as far as Bacillus spores are concerned.